: Afterdischarge in a population of neurons represent's a dramatic and wide-spread phenomenon which has been the subject of extensive investigation in many vertebrate ( for example, induced seizures in hippocampal slices) and invertebrate models. Afterdischarge can be defined as a prolonged spike activity which appears in neurons after an initial brief response to the short stimulus. This phenomenon was found in a group of electrically coupled neurons controlling prey capture reactions in the pteropid mollusc, Clione limacina. Afterdischarge activity of these neurons is a central element of feeding arousal which is the subject of a long term investigation in this model. There are two major goals of this project. The first is to investigate the mechanisms of afterdischarge using intracellular recording, voltage clamp and cell culture techniques. The second is to study the modulation of afterdischarge appearance by studying the effects of a variety of neuroactive substances and by using immunohistochemical techniques for localization of modulator containing neurons. Modulation of electrical coupling between neurons will be one of the main targets. Using all the advantages of this invertebrate model, the proposed project will give a direct answer to the question of the mechanism of afterdischarge in this network of electrically coupled neurons and will make it possible to analyze this phenomenon in relation to other systems. It will also provide information about modulatory processes in the system and bring us closer to an understanding of mechanisms of feeding arousal and the role of different neuroactive substances in its development.